基于介质碳化通道电阻与温度映射关系的光伏直流汇集系统早期故障判别

Mapping Relationship Between Carbonized Channel Resistance and Temperature Based Incipient Fault Identification Method for DC Lines

光伏中压直流汇集系统中,极间短路故障过流很可能迫使换流器在几毫秒内闭锁,保护来不及动作,引发整个系统停运。该问题可通过提前识别并隔离直流线路中的早期故障来解决。然而在直流线路上,早期故障与绝缘缺陷尚缺乏明确的边界,故障检测判据的阈值难以给定。为此,该文提出了基于碳化通道电阻与温度映射关系的早期故障边界给定原则。基于早期故障发展机理,建立了电缆早期故障实验拟合模型,选取介质碳化通道电阻为故障特征量。在计及系统电压控制约束条件下,解析电缆层间温差与碳化通道电阻的映射关系,进而确定早期故障边界。在此基础上提出了基于故障介质碳化通道电阻值的早期故障判据。仿真结果证明了早期故障边界的合理性以及早期故障判据的有效性,能够为光伏中压直流汇集系统的持续安全运行提供保障。

In the photovoltaic medium-voltage DC collection system,the short circuit fault and overcurrent force the converter to quickly lock,and cause the entire system to stop.To solve this problem,this paper realizes the identification of fault lines through the incipient fault lines.However,there is no clear boundary between incipient faults and insulation defects,so it is difficult to set the threshold value.Therefore,this paper proposes a method for incipient fault diagnosis of transmission lines based on the mapping relationship between carbonization channel resistance and temperature.The experimental fitting model of incipient fault is established,and the dielectric carbonization channel resistance is selected as the fault criterion.Considering the system voltage control constraints,the mapping relationship between the cable interlayer temperature difference and the carbonization channel resistance is analyzed to determine the initial boundary of the incipient fault and solve the problem of the unclear boundary between the incipient fault and the insulation defect.The simulation results show that the proposed method can accurately calculate the resistance value of the dielectric carbonization channel,identify and isolate the fault line,and has a specific anti-noise ability,which guarantees the continuous and safe operation of the flexible DC system.